The present invention relates to watercraft lifts and, in particular, to a watercraft cradle that is pivotally mounted to a framework and that is raised and lowered via hydraulic cylinders that are mounted above the water surface.
Numerous styles of watercraft lifts have been developed for storing a watercraft in an elevated condition above a lake, river or other waterway. Such lifts typically include a variety of linkages and frameworks that cooperate with a watercraft cradle to raise and lower the craft for use or storage. Associated awning-type covers are frequently supported to the frameworks to protect supported watercraft, such as motorboats, sail boats, personal watercraft etc., from the elements.
Many lifts provide chain or belt linkages that couple to a cradle and/or framework and are operated with the aid of a motor or hand wheel. The cradles can comprise simple slings or padded bunks that are mounted to multi-section frames and linkage arms that pivot in response to movement of a manual or electromechanical drive linkage.
A variety of lifts have also been developed that include a hydraulic linkage to raise and lower the cradle. These lifts provide a submerged cylinder that is secured to a support frame and the cradle. A reciprocating piston pivots the cradle or intervening linkage arms to raise and lower the cradle and watercraft. Several of these lifts are shown at U.S. Pat. Nos. 4,895,479; 4,900,187; 5,184,914; 5,275,505; 5,485,798; 5,908,264; 5,919,000; and 6,318,929.
Because the hydraulic cylinder of the foregoing lifts is normally submerged, a heavy-duty cylinder is required. Special care is also required to prevent infiltration of water into the cylinder, where it can mix with the hydraulic fluid. Care must also be taken to alleviate rust and pitting at the cylinder and piston, which can affect lift operation, such as by damaging provided isolation seals.
The present invention was developed to provide a hydraulically operated watercraft lift wherein a hydraulic cylinder is substantially isolated from the deleterious effects of water immersion. The cylinder is mounted to pivot from a support framework at a location where the cylinder and piston are elevated above the water. Only a distal portion of the piston is periodically submerged as a support cradle is lowered, but is wiped free of water as it is retracted.
It is accordingly a primary object of the invention to provide a watercraft lift having a hydraulic lift linkage that is normally elevated above the adjoining waterway.
It is a further object of the invention to provide a lift wherein a piston is partially submerged only as a watercraft support cradle is lowered.
It is a further object of the invention to provide a lift wherein the cylinder is mounted to pivot at a support framework.
It is a further object of the invention to provide a support framework having pivot towers that are braced by members that extend the length of the framework.
It is a further object of the invention to provide a cradle that pivots at forward and aft ends and wherein at least one hydraulic cylinder is pivotally mounted to a braced tower and to the aft end of the cradle to pivot the cradle.
It is a further object of the invention to provide bracing at the cradle and framework.
The foregoing objects, advantages and distinctions of the invention, among others, are obtained in a lift having a rectangular-shaped cradle that is secured to a surrounding support framework with H-shaped lift frames that radiate from corners of the support framework. Length adjustable legs depend from the framework to appropriately elevate and position the cradle and lift relative to the surface of the waterway. Lift towers rise from the aft or shore-end of the support framework and brace arms extend from the aft towers to the forward ends of the support framework.
A pair of hydraulic cylinders are secured to pivot at the aft lift towers and reciprocating pistons are pivotally secured to the cradle. The cylinders rotate to lie parallel to the top of the cradle when the cradle is fully elevated. When the cradle is fully lowered, the pistons are fully extended and the cylinders are rotated to an obtuse angle relative to top of the cradle. A portion of each piston is then exposed to the water. The cylinders at all times, however, remain above the water. The pistons are wiped free of water and dirt as they are extended and retracted to prevent migration of water into the cylinders and hydraulic fluid.
A variety of modifications and improvements are also disclosed that can be adapted singularly or in combination with the lift assembly.